Method and member for detecting and/or measuring the concentration of a chemical substance

Abstract

A member for detecting and/or measuring the level of concentration of a chemical substance in a medium comprises a non-metal substrate bearing a dielectric layer. A detection reactant which is capable of reacting with the substance to be detected is put on the dielectric layer and the assembly is put into the medium to be investigated, whereupon an optically detectable layer of the substance to be detected is formed on the detection reactant. The substrate is light-absorbing and one or more further dielectric layers is or are disposed between the substrate and the first-mentioned dielectric layer thereon, the thickness of the further dielectric layer or layers being such that the overall assembly comprising all the dielectric layers, the layer of detection reactant thereon and the layer of substance to be detected, is reflection-reducing in respect of non-monochromatic light which is reflected at the surface of the substrate on which the array of layers is disposed, in the wavelength range of from 525 to 600 nm.

We claim: 
     
       1. A member for detection of a chemical substance in a medium, comprising: a non-metal substrate having a surface; a first dielectric Si0 2  layer overlying said substrate; a detection reactant on the first dielectric layer and capable of reacting with the substance to be detected such that an optically detectable layer of the substance to be detected is. formed on the detection reactant upon the introduction of said member into a medium to be investigated; and at least one further dielectric layer between said surface of said substrate and the first dielectric layer and of such a thickness and with such a refractive index that in operation of the member having an overall layer array including the first and further dielectric layers, the detection reactant and thereon the layer of substance to be detected, the overall layer array operates to reduce reflection in respect of non-monochromatic light which is reflected at said surface of the substrate, in the wavelength range of from 525 to 600 nm. 
     
     
       2. A member as set forth in claim 1 wherein said detection reactant is provided on only a part of said first dielectric layer. 
     
     
       3. A member as set forth in claim 2 wherein said detection reactant is provided at a plurality of mutually separated locations on said first dielectric layer. 
     
     
       4. A member as set forth in claim 2 wherein said detection reactant is provided in an island configuration on said first dielectric layer and the island portion of detection reactant is surrounded by a layer of non-active organic substance of the same thickness and optical properties as said detection reactant. 
     
     
       5. A member as set forth in claim 1 wherein said first dielectric layer is treated with an organo-silicon compound to bind the detection reactant thereto. 
     
     
       6. A member as set forth in claim 1 wherein said detection reactant is an antigen. 
     
     
       7. A member as set forth in claim 1 wherein said detection reactant is an antibody. 
     
     
       8. A member as set forth in claim 1 wherein said detection reactant is applied to said first dielectric layer in a layer in monomolecular form. 
     
     
       9. A member as set forth in claim 1 wherein said substrate is light-absorbing. 
     
     
       10. A member as set forth in claim 1 wherein said at least one further dielectric layer has a different refractive index from said substrate and said first dielectric layer. 
     
     
       11. A member as set forth in claim 1 wherein said at least one further dielectric layer comprises Si0. 
     
     
       12. A member as set forth in claim 1 wherein said substrate has a refractive index of from about 1.45 to 1.90. 
     
     
       13. A member as set forth in claim 1 wherein said substrate comprises dark-coloured glass. 
     
     
       14. A member as set forth in claim 1 wherein said substrate comprises dark-coloured plastic material. 
     
     
       15. A member as set forth in claim 1 wherein said substrate comprises silicon. 
     
     
       16. A member as set forth in claim 1 which is in the form of a plate. 
     
     
       17. A member as set forth in claim 1 and including a layer of gel substance on said detection reactant layer. 
     
     
       18. A member as set forth in claim 17 wherein said gel layer is of a wedge-like cross-sectional configuration. 
     
     
       19. A method of detecting a biochemically reactive substance in a medium comprising: providing a detection member which includes a substrate having a surface, depositing on said surface at least one dielectric layer, depositing on said at least one dielectric layer a dielectric layer of Si0 2 , and depositing on said Si0 2  layer a layer of a detection reactant capable of reacting with the substance to be detected such that a visually discernible layer of said substance is formed on the detection reactant, the thickness and the refractive index of said at least one dielectric layer being such that the overall layer array comprising said at least one dielectric layer, said Si0 2  layer, said detection reactant layer and said layer of said substance formed thereon is at least substantially reflection-reducing in respect of non-monochromatic light which is reflected at said substrate surface in a wavelength range of 525 to 600 nm; bringing said detection member into contact with said substance to be detected in said medium whereby said visually discernible layer is formed on said member; and irradiating said detection member with non-monochromatic light to cause same to be reflected with reduced reflection at said substrate surface, thereby producing a visually discernible change in colour on at least part of said detection member bearing said layer of substance to be detected, relative to at least another part of said member, which is without said substance. 
     
     
       20. A method as set forth in claim 19 wherein said detection member has gel on its said Si0 2  layer and wherein said substance to be detected is caused to react with the layer of detection reactant by transportation in the gel on said Si0 2  layer relative to the layer of detection reactant, and the gel is removed for the visual observation step. 
     
     
       21. A method as set forth in claim 20 wherein said transportation is by diffusion effect. 
     
     
       22. A method as set forth in claim 20 wherein said transportation is by electrophoresis. 
     
     
       23. A method as set forth in claim 19 wherein the geometrical extent of the region of the detection member in which the substance to be detected is formed as a layer thereon is a measurement in respect of the concentration thereof. 
     
     
       24. A method as set forth in claim 19 wherein the geometrical extent of the region of the detection member in which the substance to be detected is formed as a layer thereon is a measurement in respect of the amount thereof. 
     
     
       25. A method as set forth in claim 20 wherein said gel has at least one recess therein for receiving a test solution containing the substance to be detected, and wherein said test solution is introduced into said at least one recess in the gel, said test solution being transported in a radial direction out of said at least one recess into the gel body. 
     
     
       26. A method as set forth in claim 20 wherein said gel is applied to said detection member in different thicknesses and the amount of the substance to be detected is determined from at least one of the factors comprising the position and the geometrical dimensions of the surface region on the detection member in which said change in colour takes place after a given reaction time. 
     
     
       27. A method as set forth in claim 26 wherein said gel is applied to said detection member in a wedge-shaped cross-sectional configuration thereon. 
     
     
       28. A member as set forth in claim 1 wherein said substrate and said further dielectric layer define a base for said Si0 2  layer, said base having a refractive index of about 2.13.